His glory is too splendid for us to see and live. The Father must hide Himself from our view, but loves us and wants to reveal Himself in some way to us.
God the Father allowed His brightness to be transformed in a way that could be safely perceptible to human beings. An outflowing of God's glory was permitted. A beam was released. It was bright enough to be recognized as God, but veiled enough to keep it from being fatal to human eyes.
Jesus is the Ray that proceeds from the central Glory, and visits us. The Son brings God the Father to us, according to the measure of our capability.
Jesus reveals the glory of the Father, as rays of our sun reveal the glory of that body. A beam from our sun is distinct from the sun; each has its own identity. Even so God the Father is not God the Son, and vice versa. But it must also be said a beam is never separate from the sun, and the sun is never without a beam. In a similar way, the Father and the Son also co-exist. Neither is ever separate from the other.
The most important comparison found in this illustration is; the sun cannot be seen except by a beam. The only way our sun communicates itself is through its rays. Likewise, the Father has hidden Himself except for what shines forth in Jesus. Only by looking at Jesus can God be seen. Without Christ, people are completely in the dark with regard to knowing God.